1. Field of Invention
This disclosure relates to earth boring reamer bits, and particularly to reamer bits configured to discharge fluids at a low impingement angle to the reamer bit cutting surface.
2. Description of Prior Art
Drill bits used in drilling of subterranean well bores typically comprise drag bits and roller cone bits. Roller cone bits typically comprise a body having legs extending downward and a head bearing extending from the leg towards the axis of the bit body. Frusto-conically shaped roller cones are rotatably mounted on each of these journals and have inserts on the outer surface of these cones. As the bit rotates, the cones rotate to cause the cutting elements to disintegrate the earth formation.
In some situations a pilot reamer drilling system is employed where two or more bits are combined on a single drill string at different vertical positions. The lower bit of the pilot reamer drilling system, which is commonly referred to as a pilot bit, creates a pilot hole. The upper bit, which follows the lower bit in the drilling process, enlarges the hole diameter over that created by the pilot bit. The bit enlarging the hole diameter is referred to as a reamer bit. Typically the pilot bit comprises a conventional earth boring bit, i.e. either a roller cone bit or a drag bit. The reamer bit usually employs rolling cutters as cutting members modified for attachment to the reamer bit body. Pilot reamer drilling systems are used to drill large diameter boreholes that require enhanced stabilization.
Drilling fluid for dispersing drilled up material and cooling the cutting elements may be injected at the cutting surfaces through nozzles. The injected fluid forms jet streams that typically are conically shaped and directed downward from the bit body. The fluid is typically injected as a high velocity jet to clean debris from drill bit cutting element thereby enhancing drilling. The dislodged particles are carried up through the borehole annulus to the surface for disposal.